The six-match suspension for the Manu hit follows a separate four-match ban he served earlier in the year for a pair of incidents in South Sydney's Round 6 clash against the Wests Tigers.
While cautioning Mitchell, Fittler stressed that the 24-year-old should not tone down his aggression too much.
"It's the aggression that sometimes makes him so brilliant," Fittler told 2GB's Wide World of Sports Radio.
"I coached him in State of Origin on the biggest stage, and without Latrell being there we're not the team that we were.
"He was brilliant, whether it was bringing it out of trouble or scoring tries, he kicked a goal from the sideline. He was outstanding and played aggressively.
"He got a tackle wrong, really wrong, and a bloke is out and paying the penalty, he's just come out of an operation and his cheekbone is going to be okay.
"At the end of the day, that's up to Latrell if he wants to do anything about it.
"The fact is, he's got plenty of judiciary problems at the moment, so the one thing he doesn't want to do is keep having to answer to the judiciary because it'll cost his team and that'll end up shortening his career."